1.搭建数据库(我用的是mysql 5.5)
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#创建一个mybatis数据库
create database `mybatis`;
#使用mybatis数据库
use `mybatis`;
#创建一个user表,有id、username、password三个字段
create table `user`(
`id` int ( 10 ) not null primary key auto_increment,
`username` varchar( 30 ) default null ,
`password` varchar( 30 ) default null
)engine=InnoDB default charset=utf8;
#插入数据
insert into `user`(`username`,`password`) values
( '张三' , 123456 ),
( '李四' , 123456 ),
( '王五' , 123456 );
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2.导入mybatis相关的jar包(COPY,建议创建一个父子项目)
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<dependencies>
<dependency>
<!--mysql依赖包-->
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version> 8.0 . 19 </version>
</dependency>
<!--mybatis依赖包-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version> 3.4 . 2 </version>
</dependency>
<!--junit依赖包,为什么要用junit依赖包? @Test 做单元测试用的-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version> 4.12 </version>
</dependency>
</dependencies>
<!--maven静态资源过滤问题:配置报错,不设置会报错:ExceptionInInitializerError-->
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>** /*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/ *.xml</include>
</includes>
<filtering> true </filtering>
</resource>
</resources>
</build>
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3.编写MyBatisUtil工具类(COPY,低层原理还没有搞懂,直接复制的条件是要创建一个mybatis-config.xml文件 文件名要一致)
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package com.kuang.utils;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class MybatisUtil {
private static SqlSessionFactory sqlSessionFactory;
static {
try {
String resource = "mybatis-config.xml" ;
InputStream inputStream = Resources.getResourceAsStream(resource);
//SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);因为重复定义导致空指针异常
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession();
}
}
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4.1编写db.properties配置文件(COPY,是后来优化的)
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driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql: //localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
username=root
password=root
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4.2编写MyBatis核心配置文件(COPY,mybatis-config.xml,已优化)
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<?xml version= "1.0" encoding= "UTF8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd" >
<configuration>
<environments default = "development" >
<environment id= "development" >
<transactionManager type= "JDBC" />
<dataSource type= "POOLED" >
<!--第一个问题:
com.mysql.jdbc.Driver和mysql-connector-java 5 一起用。
com.mysql.cj.jdbc.Driver和mysql-connector-java 6 + 一起用。
第二个问题:
serverTimezone=Asia/Shanghai 要加时区,不加时区会报错
-->
<property name= "driver" value= "${driver}" />
<property name= "url" value= "${url}" />
<property name= "username" value= "${username}" />
<property name= "password" value= "${passwprd}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource= "com/super/dao/UserMapper.xml" />
</mappers>
</configuration>
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5.编写User实体类
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public class User {
private int id; //id
private String name; //姓名
private String pwd; //密码
//构造,有参,无参
//set/get
//toString()
}
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6.编写Mapper接口类(Mapper.java)
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package com.kuang.dao;
import com.kuang.pojo.User;
import java.util.List;
public interface Mapper {
List<User> getUserList();
}
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7.编写mapper.xml配置文件
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<?xml version= "1.0" encoding= "UTF8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace= "com.super.dao.UserDao" >
<select id= "getUserList" resultType= "com.kuang.pojo.User" >
select * from mybatis.user;
</select>
</mapper>
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8.编写测试类
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package com.kuang.dao;
import com.kuang.pojo.User;
import com.kuang.utils.Mybatise;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserDaoTest {
@Test
public void test(){
SqlSession sqlSession = MybatisUtil.getSqlSession();
UserDao mapper = sqlSession.getMapper(Mapper. class );
List<User> userList = mapper.getUserList();
for (User user:userList){
System.out.println(user);
}
//sqlSession.commit();增删改需要添加事务
sqlSession.close();
}
}
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原文链接:https://blog.csdn.net/qq_41040871/article/details/114774681